<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <center>
        <p>
            <input type="text" placeholder="标题">
        </p>
        <p>
            <textarea cols="21" rows="10" value="" placeholder="请输入您的意见"></textarea>

        </p>
        <p>
            <input type="text" placeholder="手机号码">

        </p>
        <p>
            <input type="submit" value="提交" style="margin-left: 30px;width: 80px;height: 30px;" onclick="get_alert();">
        </p>
    </center>

</body>
<script>
    function get_alert() {
        alert("提交成功！");
    }
</script>

</html>